This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The aim of this project is to study polyproline helices (PP-I and PP-II) using polyprolines as model system. Standard 4-pulse DEER technique was used to measure distances between two ends of polyprolines of different sizes. The aim is to investigate the effect of pH, solvent and different spin labels on the structure of polyprolines.